District health boards in Auckland are expected to announce on Monday that part of a $560 million laboratory contract is to be handed back to the original contractor.
Diagnostic Medlab Limited (DML) lost the contract to Labtests after a long and bitter row.
Labtests took over the service early in September, but has faced criticism about delays in collecting blood from patients and reporting test results to GPs.
DHBs confirmed on Friday that they may shift up to 10% of test volumes from Labtests to DML.
The three boards are understood to have met separately on Sunday to decide whether to confirm the plan.
Radio New Zealand's health correspondent reports GPs say things have improved, but not enough.
Labtests has said the service has improved significantly and no one has been harmed.
